Motor vehicles that are propelled by internal combustion engines have electrical systems that include one or more D.C. storage batteries. In order to crank the engine at starting, an ignition switch is turned to a start, or crank, position that causes the engine to be cranked by an electric starter motor. When the engine has started, the switch is released from start position to assume a run position. In start position, electric current flows from the battery, or battery bank, to an electric starter motor that cranks the engine through a set of gears. The amount of current is typically very large, and consequently, heavy electrical cable is typically employed to conduct the current without the presence of any circuit protection device to protect against a short in the cable or the starter motor.
The electrical system has other circuits that are fed from the battery, or battery bank. Those individual circuits may be protected by their own individual circuit protection devices, such as fuses or circuit breakers, but there may be no circuit protection between the battery and the circuit protection devices themselves unless a battery disconnect switch is present.
Various types of battery disconnect switches are known. One type is a mechanical switch that requires manual operation. Because it may not be feasible to access such a switch in a hazardous situation, such as after a vehicle has been involved in an accident, automatic remote control systems for operating battery disconnect switches have been developed.
When a vehicle is equipped with a passenger airbag system, a signal that calls for airbag deployment may also be used to remotely operate a battery disconnect switch. A medium or heavy truck that may have a battery disconnect switch, typically does not have an airbag system, and so the same type of control remote control that would be present in an airbag equipped vehicle would not be present in the truck.